Hydraulic computer



1967 c. F. STEARNS HYDRAULIC COMPUTER 2 Sheets-Sheet 1 Filed May 25,1964 F'iGJ B/PAI/VCH SENSE O VAP/HBLE VAR/HEM INVENTOR CHAR LE 5 FSTEARNS BY WM ATTORNEY y 1967 c. F. STEARNS 3,317,134

HYDRAULIC COMPUTER Filed May 25, 1964 2 Sheets-Sheet 2 FIG 2 SE/VSED MZIZ u 5 is R Q X N X: 5 Lk 62 Z VHR/AIBLE INVENTOR CHARLES F'.. STEARNSATTORNEY United States Patent 3,317,134 HYDRAULIC COMPUTER Charles F.Stearns, East Longmeadow, Mass., assignor to United AircraftCorporation, East Hartford, Conn., a corporation of Delaware Filed May25, 1964, Ser. No. 369,847 7 Claims. (Cl. 235-200) This inventionrelates to hydraulic computing devices and particularly to a hydraulicsystem producing an output signal which is the product of a plurality ofvariables.

As is generally well-known in the art, multiplication of sensedvariables can be effectuated by bleeding hydraulic fluid throughsuitably disposed restrictions. The variables intended to be measuredserve to adjust the area of variable restrictions in order to controlthe pressure drop across cooperating fixed restrictions for eventuallyproducing hydraulic pressure indicative of the product of the signalssensed. The hydraulic circuitry forming the hydraulic multiplicationsystem generally comprises a network of branch parallelly disposed flowlines wherein each of the branches generally contain a fixed and avariable restriction disposed in series relationship with each other.Successive branch lines are connected intermediate the fixed andvariable restrictions and the variable restriction in each of the branchlines are varied as a function of the variable being sensed. Each of thebranch lines ultimately communicate with the drain pressure which isheld at some constant referenced pressure value. The pressureintermediate the fixed and variable restriction in the last branch isindicative of the pressure being multiplied; hence, its product. Thispressure output signal can then be ultilized as a control signal.

In the heretofore known hydraulic multiplication systems severalproblems were attendant which limited their use. One of these problemsis that the change of a variable restriction in one of the branches ofthe computing circuitry disturbs the hydraulic pressure setup by thecomputing mechanism in theadjacent branches resulting in an error.Another one of these problems is that the Reynolds number efiect throughthe various orifices owing to the changes in area produces anothererror. Still another problem is that the effective bydraulicmultiplication obtainable by one of the variables in each of thebranches is limited. This is due to the fact that if a single variablerestrictor is utilized to effectuate multiplication through asubstantial range, since the area has to vary substantially, errors arenoted in the extremity of the range.

It is, therefore, an object of this invention to obviate the problemsnoted in the immediate above paragraph.

A still further object of this invention is to provide in a hydraulicmultiplication system as described, means for switching from onevariable to another or the values in between for obtaining the productthereof.

Other features and advantages will be apparent from the specificationand claims and from the accompanying drawings which illustrate anembodiment of the invention.

FIG. 1 is a hydraulic multiplication system shown in schematicillustrating this invention.

FIG. 2 is a hydraulic schematic illustrating this invention wherein itis desired to switch between two variables or obtaining the valuetherebetween.

FIG. 3 is a graphical illustration showing the values of the variableswhich are selectively multiplied by the scheme shown in FIG. 2.

3,317,134 Patented May 2, 1967 Referring now to FIG. 1 which shows ahydraulic computing system comprising branch 1 and branch 2. Fluid isdirected from reservoir 10 through pump 12 to fixed orifice orrestriction 14 via line 16. Sensed variable 26 varies the area ofvariable orifice 18 and hence, the flow through line 16 for controllingthe pressure drop across fixed restriction 14. Fluid discharging throughvariable restriction 18 is returned to drain via line 20, drain pressureregulator generally indicated by numeral 22 and line 24. By virtue ofthe serially connected restrictions and the selection of the area ratio,the pressure intermediate fixed restriction 14 and variable restriction18 is made proportional to the value of sensed variable 26. Fluidintermediate fixed restriction 14 and variable restriction 18 isdirected through line 28 to variable restriction 30 which varies as afunction of sensed variable indicated generally by numeral 32. Variablerestrict-ion 30 serves to establish the pressure between fixedrestriction 34 and itself for establishing desired pressure in onehalfof the hydraulic network of branch 2. Fluid discharging from fixedrestriction 34 is vented to drain via line 20, drain pressure regulator22 and line 24. A portion of the fluid is directed to a branch line 36which also contains fixed restriction 38 and variable restriction 40 forestablishing the pressure in the other half of branch 2. Variablerestriction 40 serves to establish the pressure between fixedrestriction 38 and itself.

In accordance with this invention variable restriction 40 and thevariable restriction 30 are ganged so that when variable restriction 30closes, the variable restriction 40 opens a corresponding amount andvice versa. The addition of the second branch in branch 2 serves toeffectuate increased multiplication without evidencing additionalattendant errors since the impedance of the network is held at aconstant value. Since the restriction 30 is upstream of restriction 34and restriction 40 is downstream of restriction 38, the Reynolds numbereffect in the first half of branch 2 compensates the Reynolds numbereffect in the second half of branch 2. The arrangement of restrictorsminimizes the Reynolds number errors. It will be noted that by thejudicious location of valve 30 total flow through both lines 28 and 36remain constant, providing a constant impedance.

A useful output may be obtained which is indicative of the products ofthe sensed variables by suitable transducer mechanism indicated bynumeral 42. Fluid intermediate fixed restriction 38 and variablerestriction 40 is directed to the left-hand end of piston 44 via line46. The force seen by piston 44 is counteracted by the referencedpressure set up by drain pressure regulator 22 and the force created byspring 43. Hence, the movement of piston 44 is indicative of the productof the variable being sensed.

In order to effectuate multiplication hydraulically it is necessary toprovide means for maintaining the pressure upstream of orifice 14 at aconstant value. This may be done by utilizing any suitable type ofpressure regulator shown in blank by numeral 47 and to regulate thepressure of drain 20 at some constant referenced value. It is preferableto reference the drain pressure to an absolute dataum value. Drainpressure regulator 22 serves this purpose. Pressure regulator 22comprises bellows 50, pilot valve 52 and suitable flow lines to bedescribed hereinbelow. Fluid discharging from line 20 is admitted incavity 54 creating a force externally of bellows 50 opposing the forceof spring 56 located internally thereof. A portion of the fluid isadmitted into chamber 58 for acting on the upper end of pilot valve 52so that the combined forces created by the fluid in cavity 58 and theforce created by the fluid acting against spring 56 serve to positionthe pilot valve for metering fluid entering therein through line 60 andline 62 to line 24. Whenever the pressure deviates from the valuesselected by spring 56, bellows 511, sensing this deviation, positionsthe pilot valve 52 for holding the pressure in line 20 at the desiredconstant value.

As disclosed in the above description, the pressure upstream of fixedrestriction 14 is held at some constant value. Additional multiplicationmay be had by varying this pressure in accordance with another sensedvariable; as for example, structure shown in my application entitled,Hydraulic Isochronous Droop Governor, recently filed in the PatentOflice and assigned to the same assignee, may serve this purpose andreference is hereby made thereto. This application filed on May 25, 1964bears Ser. No. 369,849 and now issued as Patent No. 3,279,483. For atheoretical understanding for obtaining multiplication hydraulically,reference is also made to my application Ser. No. 337,904, filed on Jan.15, 1964, and application Ser. No. 318,671, filed on Oct. 24, 1963, nowissued as Patent No. 3,283,499, by F. E. Scheidler, both of which areassigned to the same assignee.

Next referring to FIGS. 2 and 3 which are designed to select one of twovariables or the value there-between to be multiplied in the hydrauliccomputing system. As noted in FIG. 3, it is desired to multiply thevalue of Z (raised to some exponential value). Line '60 represents thesituation where X equals an exponential value equal to T and line 62represents an exponential value where X equals S. Between line 60 andline 62 X will equal some value intermediate the values of S and T;

Now referring back to FIG. 2, all like reference numerals are identicalto the structure shown in connection with FIG. 1. For the sake ofconvenience a detailed description of like parts are omitted tofacilitate in the explanation of this invention. As noted above, thepressure in line 16 is held at some constant value. Variable restriction18 responding to some sensed variable generally indicated by numeral 26serves to regulate the pressure drop across fixed restriction 14. Thefluid is then di rected into branch 2 which comprises a pair ofparallelly disposed flow lines to be described hereinbelow. Fluidintermediate of fixed restriction 14 and variable restriction 18 isdirected to fixed restriction 62 through lines 64 and 66. Variablerestriction 68 responding to sensed variable 70 which is equal to Z asnoted in FIG. 3 serves to regulate the pressure drop across restriction62. Simultaneously, fluid in line 64 is directed to fixed restriction 72and then to variable restriction 74. Variable restriction 74 responds tosensed variable 76 which is equal to Z as indicated in FIG. 3. Bothvariable restrictions 68 and 74 may be contoured to define the functionZ +Z In that case, both restrictions will move as a function of variableZ As noted from the drawing of FIG. 2 the fluid discharging fromvariable restrictions 18, 68 and 74 discharge into drain line 20 whichis held constant to some absolute value in the same manner as wasdescribed in connection with FIG. 1.

In accordance with this invention a pair of variable restrictions 78 and80 are disposed in passage 82 which interconnects line 66 and line 64downstream of both restrictions 62 and 72. The output signal which is aproduct of the variables being sensed may be selectively made by opening78 and closing 80 or vice versa which is done manually by lever =83.Obviously, it is desirable to gang these two restrictions so that whenone opens the other closes and vice versa. The useful output signal isthen directed through line 84 to some suitable transducer mechanism asfor example the mechanism indicated by numeral 42 shown in FIG. 1. Aswas indicated above in It is to be understood that the invention is notlimited to the specific embodiment herein illustrated and described butmay be used in other ways without departure from its spirit as definedby the following claims.

I claim:

1. Means for hydraulically computing the products of sensed variablescomprising a pair of parallelly disposed fluid branches, one of saidbranches having a first flow line and a pair of serially disposedrestrictions, means for varying the area of one of said restrictions asa function of a sensed variable, the other branch having second andthird parallelly disposed fluid fiow lines each of which contain a pairof restrictions,'a drain, said second fluid flow line interconnectingsaid first fluid flow line at a point intermediate the two restrictionsin the first branch and drain, means for varying the area of theupstream restriction in said second fluid flow line as a function of asensed variable, said third fluid flow line interconnecting said drainand said second fluid flow line at a point just downstream of thevariable restriction and upstream of the other restriction disposed insaid second flow line, means for varying the area of the downstreamrestriction in said third flow line as a function of the movement ofsaid variable restriction in said second flow line and means forregulating the pressure in said drain.

2. In means as defined in claim 1 wherein said regulating meansmaintains the pressure in said drain at a constant value.

3. In means as defined in claim 1 including a pressure transducer meansand a conduit interconnecting said pressure transducer means and saidthird flow line at a point intermediate the restrictions disposedtherein.

4. In a hydraulic computing system for producing a signal commensuratewith the product of a plurality of sensed variables, a source of fluidunder pressure, a regulated pressurized drain, a first fixed and a firstvariable restriction in series relation therewith, first passage meansleading fluid from said source through said first fixed restriction,said first variable restriction to said drain, a second fixedrestriction, a second variable restriction connected in series with andlocated upstream with respect to said second fixed restriction, secondpassage means leading fluid from a point intermediate said first fixedrestriction and said first variable restriction through said secondvariable restriction, said second fixed restriction to drain, a thirdfixed restriction, a third variable restriction in series relation withand located downstream with respect to said third fixed restriction,said third variable restriction movable as a function of the movement ofthe second variable restriction and third passage means leading fluidfrom a point intermediate said second fixed restriction, said secondvariable restriction to drain.

5. In a hydraulic computing system having a source of pressure and adrain, means for regulating the pressure of said source and of saiddrain, a first passage interconnecting said source and drain, a firstfixed and a first variable restriction serially disposed in saidpassage, 21 second passage interconnecting said drain and said firstpassage at a point intermediate said first fixed restriction and saidfirst variable restriction, a second fixed restriction and a secondvariable restriction serially disposed in said second passage, a thirdpassage interconnecting said drain and said first passage at a pointintermediate said first fixed restriction and said first variablerestriction, a third fixed restriction and a third variable restrictionserially disposed in said third passage, a fourth passageinterconnecting said second passage at a point intermediate said secondfixed restriction and second variable restriction and said third passageat a point intermediate sage at a point intermediate the pair of gangedvariable restrictions.

References Cited by the Examiner UNITED STATES PATENTS 7/1964 Evans235-200 3/1966 Best 235200 RICHARD B. WILKINSON, Primary Examiner.

10 L. R. FRANKLIN, Assistant Examiner.

1. MEANS FOR HYDRAULICALLY COMPUTING THE PRODUCTS OF SENSED VARIABLESCOMPRISING A PAIR OF PARALLELLY DISPOSED FLUID BRANCHES, ONE OF SAIDBRANCHES HAVING A FIRST FLOW LINE AND A PAIR OF SERIALLY DISPOSEDRESTRICTIONS, MEANS FOR VARYING THE AREA OF ONE OF SAID RESTRICTIONS ASA FUNCTION OF A SENSED VARIABLE, THE OTHER BRANCH HAVING SECOND ANDTHIRD PARALLELLY DISPOSED FLUID FLOW LINES EACH OF WHICH CONTAIN A PAIROF RESTRICTIONS, A DRAIN, SAID SECOND FLUID FLOW LINE INTERCONNECTINGSAID FIRST FLUID FLOW LINE AT A POINT INTERMEDIATE THE TWO RESTRICTIONSIN THE FIRST BRANCH AND DRAIN, MEANS FOR VARYING THE AREA OF THEUPSTREAM RESTRICTION IN SAID SECOND FLUID FLOW LINE AS A FUNCTION OF ASENSED VARIABLE, SAID THIRD FLUID FLOW LINE INTERCONNECTING SAID DRAINAND SAID SECOND FLUID FLOW LINE AT A POINT JUST DOWNSTREAM OF THEVARIABLE RESTRICTION AND UPSTREAM OF THE OTHER RESTRICTION DISPOSED INSAID SECOND FLOW LINE, MEANS FOR VARYING THE AREA OF THE DOWNSTREAMRESTRICTION IN SAID THIRD FLOW LINE AS A FUNCTION OF THE MOVEMENT OFSAID VARIABLE RESTRICTION IN SAID SECOND FLOW LINE AND MEANS FORREGULATING THE PRESSURE IN SAID DRAIN.